Optical system and sensor for checking value documents having such an optical system
a technology of optical system and optical sensor, which is applied in the field of optical system, can solve the problems that the sensors of conventional imaging systems using only lenses or parabolic mirrors do not always meet the desired extent, and the resolution of optical sensors cannot always meet the high demands, so as to simplify the structure of optical systems and reduce scattered light
Inactive Publication Date: 2014-05-13
GIESECKE & DEVRIENT CURRENCY TECHNOLOGY GMBH
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Benefits of technology
The patent text describes an optical system that reduces geometrical errors and can be used for one-to-one imaging. The system uses a retroreflector portion that forms an intermediate image in a way that minimizes errors caused by the finite extension of the retroreflective structures and oblique incidence. The system is also compact and can be adapted to different requirements, such as greater depths of sharpness. Additionally, the system can be manufactured easily if configured suitably. Overall, the technical effects of the patent text are reduced geometrical errors, improved image quality, and a more compact and adaptable optical system.
Problems solved by technology
The optical resolution, on the other hand, need not always meet high demands.
Sensors with conventional imaging systems which employ only lenses or parabolic mirrors do not always meet these demands to the desired extent upon line-by-line imaging.
Method used
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[0037]An optical system 10 in FIG. 1 serves for imaging an object point 12 onto an image point 14. For this purpose, it possesses a plane anisotropic retroreflector portion 16, a first imaging portion 18 which produces on the retroreflector portion 16 a line-shaped intermediate image 22 of the object point 12, which lies in an object plane 20 in a specified position relative to the system 10, and a second imaging portion 24 by means of which the line-shaped intermediate image 22 is imaged into the image point 14.
[0038]The term “imaging” for the purposes of the invention also comprises here the case that the imaging is not perfectly sharp, but has a resolution limited by the components of the optical system.
[0039]The plane anisotropic retroreflector portion 16 specularly reflects radiation components 26 in a first plane of incidence 28; however, radiation components 30 in a second plane of incidence 32 are retroreflected, i.e. thrown back in the same direction from which they come, o...
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An optical system having a plane anisotropic retroreflector portion which specularly reflects radiation components in a first plane of incidence, but retroreflects radiation components in a second plane of incidence, a first imaging portion which produces on the retroreflector portion a line-shaped intermediate image of an object point in an object plane in a specified position relative to the system, the image extending along a line in the second plane of incidence, and a second imaging portion by means of which the line-shaped intermediate image is imaged into an image point.
Description
BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to an optical system, in particular an imaging optical system, a sensor for checking value documents with such an optical system, and a method for imaging an object point.[0003]2. Related Art[0004]Value documents are understood in this connection to be sheet-shaped objects that represent for example a monetary value or an authorization and hence should not be producible arbitrarily by unauthorized persons. Hence, they have features that are not easily produced, in particular copied, whose presence is an indication of authenticity, i.e. production by an authorized body. Important examples of such value documents are cards, coupons, vouchers, checks and in particular bank notes. Bank notes for the purposes of the invention are sheet-shaped.[0005]Optical systems in general will hereinafter be understood to be systems that influence optical radiation, in particular changing its ray trajectory. ...
Claims
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Login to View More IPC IPC(8): G03B21/28
CPCG02B5/045G02B17/0804G07D7/121
Inventor WUNDERER, BERND
Owner GIESECKE & DEVRIENT CURRENCY TECHNOLOGY GMBH